OpAmp as D/A convertor help needed.

Discussion in 'The Projects Forum' started by Mussawar, Aug 11, 2013.

  1. Mussawar

    Thread Starter Member

    Oct 17, 2011
    I have to convert 10 bit binary code to analog value. Special ICs for this purpose are out of reach for me. I have collected some circuits from different sites. Please take a look at attachment and recommend which circuit seems batter.
    Can I extend it to 10 bits by adding more resisters with same ascending order? I’m using single 9v power supply for my entire circuit.
    Further more, I have to make 4 sets of this D/A converter, so can I replace 741 with LM324 (4 OpAmps in one chip). Please help and guide me anymore about this.
  2. bertus


    Apr 5, 2008
  3. Mussawar

    Thread Starter Member

    Oct 17, 2011
    Yes, it seems more easy. Can I use this one instead? Please look at atachment. 7493 might be some thing else. Would it be fine with single supply?
  4. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
    May I ask what you're planning to use it for?
  5. ramancini8


    Jul 18, 2012
    Resistor tolerances, op amp offsets, noise, and leakage currents almost guarantee that you will not get to 10 bits accuracy.
  6. Mussawar

    Thread Starter Member

    Oct 17, 2011
    I want to use it as a reference for a 741 comparator. Second input of the comparator would be a sensor's signal. In detail, for comparator, first input is a sensor giving analog out from 0 to 9v. Second input (reference) is this D/A convertor' output. I want to compare sensor's signal and D/A output. I want to operate a relay when both inputs are equal.
  7. Mussawar

    Thread Starter Member

    Oct 17, 2011
    I need 5% accuracy. Can you point out some thing else?
  8. WBahn


    Mar 31, 2012
    Then why are you trying to make a 10-bit DAC. All you need is at least a 5-bit DAC, which has nominal steps that are about 3% apart. An 8-bit DAC will giet you better than 0.5% steps, an order of magnitude better than what you say you need.

    Why are special ICs for this purpose out of reach for you? Cost?

    You can buy a 10-bit DAC from Digi-Key for under $1 and a quad 10-bit DAC for under $5. You can get quad 8-bit DACs for under $3. And these are at Digi-Key onezy prices! Your cost for an opamp and the resistors is probably going to total more than the DAC.

    Now, you haven't given anywhere near enough information to tell if the cheap end of the DAC selection will actually work for you. But if you are willing to work with us to flesh out your constraints, we can probably find a suitable DAC that fits your budget.